The present invention relates to a finger-pressure cushioning and indicating device for application to a finger-pressure actuated article. The invention is particularly useful with respect to syringes, and is therefore described below in connection with such an application, but it will be appreciated that the invention could advantageously be used in other applications as well, whenever an object is to be actuated by controlled pressure applied by a finger, hand, or the like.
Syringes commonly include a cylinder having a liquid discharge opening at one end through which the liquid contained within the cylinder is ejected, the ejection being effected by means of a plunger assembly having a piston at one end displaceable in the cylinder, and a pressure-applying element at the opposite end projecting exteriorly of the cylinder. The arrangement is such that the user holds the cylinder between two fingers and applies a third finger, namely his thumb, to the pressure-applying element of the plunger assembly, thereby to displace the piston within the cylinder and to discharge liquid through the cylinder opening.
One of the disadvantages of the known syringes, however, is that, because of the different designs, constructions and sizes of such syringes now on the market, it is very difficult, if possible at all without the use of a manometer or other pressure-measuring instrument, for the user to be aware of the pressure he is applying for injecting the liquid into the patient's body. This can be quite dangerous, since an excessively high pressure can cause rupture of the patient's vein. For this reason, many infusions are effected not by syringes, but rather by gravity-operated influsion sets, but such procedures require a considerably longer period before the fluid being injected becomes effective, which again can be detrimental to the health of the patient.